Yarn severing and clamping mechanism for knitting machines



July 3.4, 1970 J, LAWSON 3,520,154

YARN SEVERING AND CLAMPING MECHANISM FOR KNITTING MACHINES Filed Dec. 11, 1967 t3 Sheets-Sheet 1.

) 43 Fig.

20b I60. I

22 INVENTOR.

W- JOHN B. LAWSON 2 I I7 BY ATTORNEYS.

.Bufiy 14, 1970 J. a. LAWSON 3,520,154

YARN SEVERING AND CLAMPING MECHANISM FOR KNITTING MACHINES Filed Dec. 11, 1967 2 Sheets-Sheet I? INVENTOR.

a JOHN B. LAWSON ATTORNEYS.

United States Patent 3,520,154 YARN SEVERING AND CLAMPING MECHANISM FOR KNITTING MACHINES John B. Lawson, 368 New Meadow Road, Barrington, RI. 02806 Filed Dec. 11, 1967, Ser. No. 689,588 Int. Cl. D04b 15/61 U.S. Cl. 66140 Claims ABSTRACT OF THE DISCLOSURE A yarn trimmer having a pneumatically powered cutting mechanism controlled by a yarn activated trigger. A yarn clamping mechanism comprising spaced apart blades cooperates with the trimmer, the blades having lower flexible portions biased against a plate at an angle of less than 90. I

This invention relates to yarn trimmers and clamping mechanisms for knitting and other textile or strandutilizing machines.

CROSS-REFERENCE TO RELATED APPLICATIONS There are no related applications.

BRIEF SUMMARY OF THE INVENTION The yarn trimmer of, this invention is primarily for use with circular knitting machines having two or more yarn feeding fingers at one or more knitting stations.

In many uses of such machines, such as knitting halfhose and the like, it is desirable to knit yarns of different characteristics in alternation at a given feeding location. For example, it is often desirable to knit yarn of a first color and then change to knitting with yarn of another color.

In order to change from one yarn to another during knitting, the yarn feeding finger then feeding a yarn to the needles is withdrawn, usually by elevating the same. At the same time, another yarn feeding finger, carrying a different yarn, is moved into the active (feeding) position, usually by lowering the same, so that the needles will take and knit such yarn.

After a yarn finger is withdrawn from active position, it is desirable to sever the yarn at some point between the feeding finger and the fabric, and to hold the severed end. In order to accomplish this severing function, various types of mechanical yarn trimmers have been designed.

One primary difficulty with many prior art trimmers, however, is that they require elaborate timing mechanism for controlling the action of the cutting means for the yarn. For example, many of such devices are controlled through linkage activated by cams on the main pattern drum of the knitting machine.

The primary object of the present invention is to provide a yarn trimmer for circular knitting machines having two or more yarn feeding fingers per knitting station wherein the cutting mechanism is pneumatically powered and under the control of a yarn activated trigger mechanism, so that expensive and cumbersome timing mechanism connected to other parts of the knitting machine is unnecessary.

As will be observed, another feature of the present invention is that the trimmer mechanism is an integral unit and portable in nature so that it may easily be removed from one knitting machine and placed on another as the situation may require.

Another feature of the yarn trimmer of this invention is a novel clamping means comprising a plurality of spaced apart, thin metallic blades, the lower portions of which are disposed at an angle with respect to the surface of the trimmer plate. Using this arrangement, a very efficient holding action is achieved which prevents withdrawal of the yarn from under the clamp.

Although the invention is specifically disclosed primarily in connection with knitting machines to exemplify a preferred embodiment, the yarn or strand severing mechanism and clamping means are broadly applicable to other types of textile and strand utilizing machinery such as looms, sewing machines, braiding devices, etc.

DRAWINGS In the drawings:

FIG. 1 is a perspective view of one embodiment of the yarn trimmer of this invention as it is used in connection with a circular knitting machine of a single feed type.

FIG. 2 is another perspective view of the yarn trimmer shown in FIG. 1, taken from the opposite side of the knitting cylinder.

FIG. 3 is a perspective view of the yarn trimmer shown in FIG. 1 taken from approximately the right side of FIG. 1.

FIG. 4 is a horizontal sectional view taken along the lines of IV-V of FIG. 3; and

FIG. 5 is a fragmentary view in elevation of the lower part of the trimmer mechanism showing in detail the angular position of the clamping blades.

DETAILED DESCRIPTION Turning to FIG. 1, there is shown the sinker ring 10 of a circular knitting machine, together with associated sinkers 11 and needles 12. At the knitting station, shown at the left in FIG. 1, there is a pair of yarn fingers 13, 14, for yarns 15, 16. As shown, finger 13 is in the lower, active position where it is feeding yarn 15 to the needles 12.

As shown in FIG. 1, the yarn finger 14 has just been raised to the inactive position. The last needle 12a to knit yarn 16 has carried the yarn halfway around the cylinder in the usual counterclockwise direction and, as a result, yarn 16 has been pulled under the blades 18 of a clamp 17 which bear upon a binder plate 20.

As shown best in FIG. 5, yarn clamp 17 consists of a plurality of resiliently flexible thin metal blades 18 and intervening spacers 19 which are held in fixed position above binder plate 20 by means of a screw stud 21 secured to a bearing 22 on an upright bracket 23 in FIG. 2. The lower portions of blades 18 are disposed at an angle to plate 20 and are sufiiciently flexible to be moved away from the vertical to permit a yarn, such as yarn 16, to pass thereunder when a yarn feeding finger is raised out of action. However, once a yarn passes under the clamp 17, the pressure of the spring blades 18 prevent the yarn from withdrawing in the direction of the feeding finger from which it extends. These clamps thus create what may be termed a saw-toothed holding action on the yarn which is superior in efficiency to clamps which are now known to the art. Due to the angular disposition of the blades 18, any attempt by the yarn to withdraw toward the feeding finger pulls the blades 18 against the binder plate 20 and thus creates an additional holding action on the yarn. As best shown in FIG. 5, the angle formed between the plane of the blades 18 and the surface of the plate 20 with the apex defined by the lower edge of the blades 18 is less than It is thus a novel feature of the clamping means of this invention that the holding action created by such means increases in direct proportion to the withdrawal forces on the yarn in the direction of the feeding finger from which the yarn extends. On the other hand, the arrangement of blades 18 is such 3 that when a yarn is pulled from a direction opposite the feeding fingers, the blades tend to swing up and away from the binder plate, in a movement similar to that of a hinge, and the yarn will easily withdraw from under the blades providing a ready release of the yarn in that cylinder rotation direction.

Binder plate 20 is maintained approximately in the center of the needle cylinder by means of bracket 23. The latter is a lower extension of trimmer power unit 24 which is supported by a bracket 25 secured to the frame of the machine.

The trimmer mechanism includes a movable cutter blade 26 and a fixed blade 27. The latter is held by stud 21 in slot 20a in plate 20 and has an upper cutting edge which slopes downwardly toward the periphery of the plate 20. Thus, when a withdrawn yarn, such as yarn 16, is held by clamp 17 the progressive counterclockwise movement of the last needle 12a to 'which the yarn is connected carries the tail 16a of the yarn over the edge of the blade 27.

Blade 26 is pivotally mounted on stud 21 whereby on clockwise movement the sharp front lower edge of blade 26 is moved past the opposing edge of blade 27 to cut any yarn, such as yarn 16, lying across the latter.

Movement of the blade 26 is effected by a piston 28 in the power unit 24 via a link 29 which is secured for pivotal motion to bracket 23 by a stud 30. At its upper end, link 29 is connected by a pin 31 to extension 28a of piston 28. The lower bifurcated end of link 29 embraces a screw 32 attached to the upper portion of blade 26. Thus, movement of piston 28 to the rear of the power unit 24 (i.e., to the left in FIG. 2) Will cause the front of knife blade 26 to descend in the cutting movement described; movement of the piston in the opposite direction will, of course, cause the front of the blade to rise to the inactive position shown in FIG. 1.

Power unit 24 includes a rear casing 33 (of which bracket 23 is a lower extension) having its mid-section removed to accommodate piston 28, link 29, and the other mechanism shown in FIG. 2. The front of the unit comprises a head 34 with a cylindrical portion 34a. Head 34 is secured to casing 33 by bolts, as indicated in FIG. 3.

An air space or chamber 35 is formed between the head 34 and the opposing face of piston 28, and this chamber is hermetically sealed by a flexible circular Bellofram membrane 36 the center of which is secured to the head of piston 28 by a circular plate 37 attached to the piston by a screw 38, and the edge of which is locked between the opposing edges of casing 33 and head 34.

Compressed air or another suitable pressure medium is injected (from a source not shown) into chamber 35 through a supply nozzle 39 which reduces to a 0.010 inl t orifice 40. At the other side of the chamber, there is a nozzle 41 terminating in a 0.030" outlet orifice 42.

As shown in FIG. 3, the trimmer is provided with a yarn sensing arm or trigger 43 which regulates the air pressure in chamber 35 and thus controls the movement of piston 28 and, through the latter, the movement of cutter blade 26. Trigger 43 is pivotally attached at 44 to casing 33 with its lower end extending through a slot 20b in plate 20. The trigger is equipped at its upper end with a resilient bumper 43a which completely seals off orifice 42 upon counterclockwise movement of the trigger 43. Trigger 43 is light and so delicately balanced that air normally escapes freely through orifice 42, blowing bumper 43a away. Since the area of orifice 42 is nine times larger than inlet 40, there is no pressure buildup in chamber 35 in such normal condition.

As shown in FIG. 2, a bar 45 attached to the rear of casing 33 carries a set screw 46 supporting a spring 47 which bears against extension 28a of piston 28. As long as air escapes freely from orifice 42, spring 47 maintains piston 28 at the front of chamber 35 against the inside wall of cylinder head 34. In this position, the lower part 4 of link 29 is thrust to the rear, thus maintaining cutter blade 26 in the raised inactive position shown.

When a yarn finger is raised out of action, its yarn is carried under the clamp 17 and over fixed blade 27, as indicated in FIG. 1 in connection with yarn finger 14 and yarn --16. As the needles continue to turn, the yarn portion 16a between the clamp and the fabric is pulled against trigger 43. As a result, the trigger pivots in a counterclockwise direction and its bumper valve 43a closes orifice 42.

Upon the closing of orifice 42, there is a rapid increase in pressure in chamber 35 which quickly overcomes the opposing force of spring 47 so that piston 28 is moved rearwardly. The lower end of link 29 is rocked forward, moving the front of blade 26 downward to cut the tail of yarn 16a between the clamp and fabric. When the yarn is severed, trigger 43 is released and swings back to its normal position whereby air escapes freely from the chamber 35. Upon the reduction of pressure in the chamber, piston 28 moves toward the front of the power unit housing under the influence of spring 47, whereby, via link 29, knife 26 is raised to the normal inactive position and the trimmer is ready for the next change of yarn.

vIt should be made clear that I have described but an embodiment of my invention, and that the principles thereof may be utilized in a number of forms.

Having thus described my invention, I claim:

1. A yarn trimmer for a circular knitting machine having means to withdraw a selected yarn from knitting as desired, comprising in combination:

(a) A cutter plate,

(b) A clamp comprising spaced apart blades having lower flexible portions, and support means for maintaining said lower flexible portions biased against said plate at an angle of less than with respect thereto for holding said selected yarn against the plate upon withdrawal whereby any force upon the yarn opposite the direction of inclination of the lower portions of the blades pulls the blades with greater force against the plate and the yarn clamped therebetween, and so that any withdrawal force upon the yarn in the direction of inclination of the lower portions of the blades pulls the blades up and away from the plate so that the yarn is easily released from the clamp,

(c) A yarn cutter, having a movable blade, disposed adjacent the clamp,

(d) A power unit for moving said movable blade,

(e) A control trigger disposed in the path of the selected yarn and operable to activate the power unit upon contact with the selected yarn as it is carried across the plate by the fabric.

2. A knitting machine yarn trimmer mechanism including a binder plate, means for severing yarn adjacent said plate, and yarn clamping means for the severed yarn comprising spaced apart blades having lower flexible portions and support means for maintaining said lower flexible portions biased against said plate at an angle of less than 90 with respect to said binder plate for holding said severed yarn against the plate whereby any force upon the yarn opposite the direction of inclination of the lower portions of the blades pulls the blades with greater force against the plate and the yarn clamped therebetween, and so that any withdrawal force upon the yarn in the direction of inclination of the lower portions of the blades pulls the blades up and away from the plate so that the yarn is easily released from the clamp.

3. In a knitting machine having needles and means for feeding yarns thereto, and means for severing said yarns, yarn clamping means for retaining said severed yarns comprising:

(a) A binder plate supported adjacent the needles, said plate including a top surface,

(b) A plurality of spaced apart clamping blades, each including a flexible lower portion having a lower edge, and

(c) Means for holding the lower portions of the blades pressed against the top surface of the plate in angular relationship thereto with the lower edges of the blades in contact with said surface, said angular relationship being less than 90, as defined by the relationship of the plane of said lower portions and the surface of the plate with the lower edge of the lower portions as the apex whereby any force upon the yarn opposite the direction of inclination of the lower portions of the blades pulls the blades with greater force against the plate and the yarn clamped therebetween, and so that any withdrawal force upon the yarn in the direction of inclination of the lower portions of the blades pulls the blades up and away from the plate so that the yarn is easily released from the clamp,

4. A yarn trimming mechanism for a knitting machine having yarn feeding means for withdrawing a selected yarn from knitting comprising:

(a) Severing means for severing the selected yarn, said means including a movable cutter element,

(b) A power unit for moving said movable cutter element including:

(i) A housing having a hermetic interior chamber having intake and outlet orifices for compressed air, wherein said outlet orifice is larger than said inlet orifice,

(ii) A piston movable within said chamber,

(iii) Linkage means connecting said piston and said movable cutter element whereby movement of the piston moves the element,

(iv) Means normally biasing the piston into the chamber,

(v) Valve means for the outlet orifice normally operative to maintain the air pressure within the chamber in equilibrium with the force biasing the piston into the chamber, whereby the piston and connected cutter blade are normally motionless,

(c) A control trigger having one portion disposed in the path of the yarn being withdrawn from knitting and another portion connected to said outlet orifice 6 valve means and operative to move the same to close said orifice when the withdrawing yarn contacts the trigger, whereby the air pressure within the chamber is caused to exceed the force biasing the piston inwardly, whereby the piston moves the cutter element to sever the yarn being withdrawn,

((1) and means for clamping the withdrawn yarn.

5. The invention of claim 4 wherein the yarn trimming mechanism includes a binder plate and the means for 10 clamping the withdrawn yarn comprises:

(a) A plurality of blades, each having a flexible lower portion, and (b) Support means connected to said blades for maintaining them in substantially parallel, spaced apart relation to each other and for holding the lower portions thereof pressed against the binder plate at less than a angle, as defined by the relationship of the plane of said lower portions and the surface of the plate, whereby withdrawn yarn extending from the feeding means therefor is clamped against the plate by the blades so that any withdrawal force upon the yarn toward the feeding means pulls the blades with greater force against the plate and the yarn clamped therebetween, and so that withdrawal force upon the yarn from the side opposite said feed ing means, upon reactivation of the latter, pulls the blades up and away from the plate whereby the yarn is easily released from the clamp.

References Cited UNITED STATES PATENTS 2,952,148 9/1960 Rather 66145 XR 1,945,971 2/1934 Gagne 66145 2,287,131 6/ 1942 Redeen 66140 3,055,199 9/ 1962 Stack. 3,090,217 5/1963 Ziemba et a1 66140 3,092,986 6/1963 Moyer 66140 FOREIGN PATENTS 1,019,969 2/1966 Great Britain.

580,759 8/ 1958 Italy.

ROBERT R. MACKEY, Primary Examiner 

